At present, as more users are using wireless local area network (WLAN) for data communications, the load of the WLAN networks is increasing, and as the number of users is increasing, the efficiency of the WLAN networks is also tending to decline significantly. Taking measures to merely increase the rate thereof cannot solve the abovementioned problems. Multi-station parallel transmission, as an alternative technology to improve network efficiency, has aroused extensive attentions and researches. In the related art, multi-station parallel transmission technologies may comprise, but are not limited to, Multi-User Multiple-Input Multiple-Output (MU-MIMO) technology (i.e., spatial domain multiple access), Orthogonal Frequency Division Multiple Access (OFDMA) technology (i.e., frequency domain multiple access).
FIG. 1 is a schematic diagram of a WLAN basic service set according to the related art. As shown in FIG. 1, in a WLAN, an access point station (AP STA) and a plurality of non-AP stations (non-AP STAs) associated with the AP form a basic service set (BSS).
In order to solve hidden station problems, 802.11 has proposed a virtual channel detection mechanism: when station 1 sends a frame, the frame it sends may carry a time domain) to indicate the length of time required by the station to complete the frame exchange. Station 2 receives the frame sent by station 1 and returns a response frame, wherein the response frame also carries a time domain to ensure that station 1 can complete the frame exchange. Other listening stations that have heard the frame exchange may configure a network allocation vector (NAV), and the value of the NAV may be configured to be the maximum value in the abovementioned time domain. During this time, the listening stations will not send data, thus avoiding collisions caused by hidden nodes contending for channels. Other stations can send data only after the NAV is decreased to zero.
FIG. 2 is a schematic diagram of multi-station transmission frame exchange according to the related art. As shown in FIG. 2, the multi-station parallel transmission in a WLAN usually shows multiple non-AP STAs simultaneously send data to an AP, which is generally referred to as an uplink multi-user (UL MU) transmission, or the AP sends data to multiple non-AP STAs simultaneously, which is referred to as a downlink multi-user (DL MU) transmission. FIG. 2 shows a typical uplink and downlink multi-station transmission frame exchange sequence.
In the technical solution provided in the related art, a UL MU transmission needs an AP to trigger, for example, by sending a trigger frame to trigger, or by means of a radio frame carrying a trigger information domain to trigger. The trigger frame or trigger information domain carries the scheduling information of the station, for example, the identification information of the station, time and frequency resource information used by the station for uplink transmission, time-frequency offset calibration information of the station, and the like. After the AP has sent the trigger frame or trigger information domain, the station receives the trigger frame or trigger information domain, if its own identification information is carried therein, which indicates that it itself is scheduled in this UL MU transmission, and if it itself has data to send, it may prepare and synchronize according to the time-frequency offset calibration information indicated by the AP, to send the data on the allocated time and frequency resources.
The multi-station transmission allows for multi-station parallel transmission, thereby saving the time for which the air interface is occupied. In a network user-intensive scenario, network collisions can be reduced and air interface efficiency can be improved. Future WLAN communication systems can support continuous and non-continuous bandwidth distribution of 20 MHz/40 MHz/80 MHz/160 MHz. If some station obtains certain channel resources by contention but the station itself occupies only a part of the channel resources for transmission, as all the bandwidth resources obtained by contention have been claimed by the station for occupation, other stations are unable to contend for occupation. However, the problem is that the station does not actually occupy all the resources, and thereby causes the waste of frequency resources. The related art has not provided an effective solution to the abovementioned technical problems.
This section provides background information related to the present disclosure which is not necessarily prior art.